This invention relates to a solid state relay and, more particularly, to a solid state relay in which a light emitting diode converts an input signal to a light signal, a photovoltaic diode array optically coupled to the light emitting diode converts the light signal to an electrical signal which is used for driving a metal-oxide-semiconductor field effect transistor (hereinafter reffered to simply as "MOSFET") as an output means to obtain a contact signal as an output.